AttributedString+RegularExpression.swift

extension NSMutableAttributedString {
    
    static func generateAttributedString(with searchTerm: String, targetString: String) -> NSMutableAttributedString? {

        let attributedString = NSMutableAttributedString(string: targetString)
        do {
            
            // Your more complicated expressions here
            let regex = try NSRegularExpression(pattern: searchTerm, options: .caseInsensitive)
            
            let range = NSRange(location: 0, length: targetString.utf16.count)
            for match in regex.matches(in: targetString, options: .withTransparentBounds, range: range) {
                attributedString.addAttribute(NSAttributedString.Key.font, value: UIFont.systemFont(ofSize: 16, weight: UIFont.Weight.bold), range: match.range)
            }
            
            return attributedString
        } catch {
            print("Error creating regular expresion: \(error)")
            return nil
        }
    }
}